US8957998B2ActiveUtilityA1
Lens shading correction apparatus and method in auto focus camera module
Est. expiryDec 14, 2029(~3.4 yrs left)· nominal 20-yr term from priority
Inventors:Jinwook Hyun
H04N 25/61H04N 23/67H04N 23/63H04N 5/3572
59
PatentIndex Score
3
Cited by
9
References
17
Claims
Abstract
Provided is a lens shading correction method, the lens shading correction method including, obtaining optical axis coordinates and a center-contrasted surrounding gain according to a lens position of a predefined long-distance focusing and short-distance focusing to a sample image input in which each pixel has an uniform brightness value, obtaining image data using the auto focus function, obtaining a modified optic coordinate and center-contrasted surrounding gain according to a lens position used in the acquisition of the image data, and lens shading correcting the image data using the modified optic axis coordinate and center-contrasted surrounding gain.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A lens shading correction method, the method comprising:
determining a first optical center coordinate at an image sensor and a first gain corresponding to a first position of a lens, and a second optical center coordinate at the image sensor and a second gain corresponding to a second position of the lens related to a sample image in which each pixel has a uniform brightness, the first position including a long-distance focusing position and the second position including a short-distance focusing position;
obtaining an image by the image sensor;
determining a third position of the lens when the image is obtained;
determining a third optical center coordinate at the image sensor and a third gain corresponding to the third position of the lens; and
compensating the image by the third optical center coordinate and the third gain;
wherein the third optical center coordinate is determined by the first and second optical center coordinates and the third gain is determined by the first and second gains; and
wherein the third optical center coordinate at the image sensor is determined based on the coordinates of the first and second optical centers in relation to the first, second, and third lens positions.
2. The method of claim 1 , wherein an x-coordinate of the third optical center coordinate is determined by following equation:
center
X
(
d
)
=
(
d
-
min
)
×
(
CX
max
-
CX
min
)
(
max
-
min
)
+
CX
min
,
where d is the third position of the lens; min is the first position of the lens; max is the second position of the lens; CXmin is an x-coordinate of the first optical center coordinate; CXmax is an x-coordinate of the second optical center coordinate; and centerX(d) is the x-coordinate of the third optical center coordinate.
3. The method of claim 1 , wherein a y-coordinate of the third optical center coordinate is determined by following equation:
center
Y
(
d
)
=
(
d
-
min
)
×
(
CY
max
-
CY
min
)
(
max
-
min
)
+
CY
min
,
where d is the third position of the lens; min is the first position of the lens; max is the second position of the lens; CYmin is a y-coordinate of the first optical center coordinate; CYmax is an x-coordinate of the second optical center coordinate; and centerY(d) is the y-coordinate of the third optical center coordinate.
4. The method of claim 1 , wherein the third gain is determined by following equation:
Gain
(
d
)
=
(
d
-
min
)
×
(
G
max
-
G
min
)
(
max
-
min
)
+
G
min
,
where d is the third position of the lens; min is the first position of the lens; max is the second position of the lens; Gmin is the first gain; Gmax is the second gain; and Gain(d) is the third gain.
5. A lens shading compensation method, the method comprising:
determining a first optical center coordinate at an image sensor and a first gain corresponding to a first position of a lens, and a second optical center coordinate at the image sensor and a second gain corresponding to a second position of the lens, the first position including a long-distance focusing position and the second position including a short-distance focusing position;
obtaining an image by the image sensor;
determining a third position of the lens when the image is obtained;
determining a third optical center coordinate at the image sensor and a third gain corresponding to the third position of the lens; and
compensating the image by the third optical center coordinate and the third gain;
wherein the third optical center coordinate is determined by the first and second optical center coordinates and the third gain is determined by the first and second gains; and
wherein the third position optical center coordinate at the image sensor is determined based on the coordinates of the first and second optical centers in relation to the first, second, and third lens positions.
6. The method of claim 5 , wherein the obtaining an image by the image sensor includes obtaining the image by the image sensor and by the lens using an auto focus function.
7. The method of claim 5 , wherein the first and second optical center coordinates and the first and the second gains are related to a standard image where each pixel has a uniform brightness.
8. The method of claim 5 , wherein an x-coordinate of the third optical center coordinate is determined by following equation:
center
X
(
d
)
=
(
d
-
min
)
×
(
CX
max
-
CX
min
)
(
max
-
min
)
+
CX
min
,
where d is the third position of the lens; min is the first position of the lens; max is the second position of the lens; CXmin is an x-coordinate of the first optical center coordinate; CXmax is an x-coordinate of the second optical center coordinate; and centerX(d) is the x-coordinate of the third optical center coordinate.
9. The method of claim 5 , wherein a y-coordinate of the third optical center coordinate is determined by following equation:
center
Y
(
d
)
=
(
d
-
min
)
×
(
CY
max
-
CY
min
)
(
max
-
min
)
+
CY
min
,
where d is the third position of the lens; min is the first position of the lens; max is the second position of the lens; CYmin is a y-coordinate of the first optical center coordinate; CYmax is an x-coordinate of the second optical center coordinate; and centerY(d) is the y-coordinate of the third optical center coordinate.
10. The method of claim 5 , wherein the third gain is determined by following equation:
Gain
(
d
)
=
(
d
-
min
)
×
(
G
max
-
G
min
)
(
max
-
min
)
+
G
min
,
where d is the third position of the lens; min is the first position of the lens; max is the second position of the lens; Gmin is the first gain; Gmax is the second gain; and Gain(d) is the third gain.
11. A lens shading compensation apparatus, comprising:
a lens unit configured to perform an auto focusing, the lens unit comprising a plurality of lenses;
an image sensor configured to convert an optical signal from the lens unit to an image;
a memory configured to store a first optical center coordinate at the image sensor and a first gain corresponding to a first position of the lens unit, and a second optical center coordinate at the image sensor and a second gain corresponding to a second position of the lens related to a sample image in which each pixel has a uniform brightness, the first position including a long-distance focusing position and the second position including a short-distance focusing position;
a modification unit configured to:
determine a third position of the lens unit when the image is obtained, and
determine a third optical center coordinate at the image sensor and a third gain corresponding to the first position of the lens unit; and
a processing unit configured to compensate the image by the third optical center coordinate and the third gain;
wherein the modification unit is further configured to determine the third optical center coordinate by the first and second optical center coordinates and determine the third gain by the first and second gains; and
wherein the modification unit is further configured to determine the third optical center coordinate at the image sensor based on the coordinates of the first and second third optical centers in relation to the first, second, and third lens positions.
12. The apparatus of claim 11 , further comprising:
a display unit configured to display a compensated image.
13. The apparatus of claim 12 , wherein the display includes a liquid crystal display (LCD) or an organic light emitting device (OLED).
14. The apparatus of claim 11 , wherein the apparatus is equipped in a portable phone.
15. The apparatus of claim 11 , wherein an x-coordinate of the third optical center coordinate is determined by following equation:
center
X
(
d
)
=
(
d
-
min
)
×
(
CX
max
-
CX
min
)
(
max
-
min
)
+
CX
min
,
where d is the third position of the lens unit; min is the first position of the lens unit; max is the second position of the lens unit; CXmin is an x-coordinate of the first optical center coordinate; CXmax is an x-coordinate of the second optical center coordinate; and centerX(d) is the x-coordinate of the third optical center coordinate.
16. The apparatus of claim 11 , wherein a y-coordinate of the third optical center coordinate is determined by following equation:
center
Y
(
d
)
=
(
d
-
min
)
×
(
CY
max
-
CY
min
)
(
max
-
min
)
+
CY
min
,
where d is the third position of the lens unit; min is the first position of the lens unit; max is the second position of the lens unit; CYmin is a y-coordinate of the first optical center coordinate; CYmax is an x-coordinate of the second optical center coordinate; and centerY(d) is the y-coordinate of the third optical center coordinate.
17. The apparatus of claim 11 , wherein the third gain is determined by following equation:
Gain
(
d
)
=
(
d
-
min
)
×
(
G
max
-
G
min
)
(
max
-
min
)
+
G
min
,
where d is the third position of the lens unit; min is the first position of the lens unit; max is the second position of the lens unit; Gmin is the first gain; Gmax is the second gain; and Gain(d) is the third gain.Join the waitlist — get patent alerts
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